In an Angular application a FormControl has errors hanging off of it as a property.

"ASP.NET Core 2 and Angular 5" by Valerio De Sanctis mentions this on page 336. It suggests that required hanging off of errors as in errors.required will be true if there is an error of that specific shape with the FormControl. This suggests errors is of a type called ValidationErrors (or just null) and this further suggests other Boolean properties off of errors like errors.email and errors.minlength too. Both of the links I give here are going to be for versions of Angular beyond Angular 5 however.